PHP, Ruby, Groovy have spaceship operator `<=>`. In short, this operator compares values and returns `1`, `-1`, `0`.
ECMAScript spec's `TypedArray#sort` has the default comparison part like following code, so I think it's useful that appending spaceship operator to ECMAScript like it. http://www.ecma-international.org/ecma-262/8.0/#sec-%typedarray%.prototype.sort ```javascript function isPlusZero(val) { return val === 0 && 1 / val === Infinity; } function defaultCompare(x, y) { const [isNaN_x, isNaN_y] = [Number.isNaN(x), Number.isNaN(y)]; if(isNaN_x && isNaN_y) return 0; if(isNaN_x) return 1; if(isNaN_y) return -1; if(x < y) return -1; if(x > y) return 1; if(x === 0 && y === 0) { const [isPlusZero_x, isPlusZero_y] = [isPlusZero(x), isPlusZero(y)]; if(!isPlusZero_x && isPlusZero_y) return -1; if(isPlusZero_x && !isPlusZero_y) return 1; } return 0; } ``` ```javascript // NaN behave like the biggest number NaN <=> NaN // 0 NaN <=> 42 // 1 42 <=> NaN // -1 Infinity <=> NaN // -1 // finite 10 <=> 10 // 0 -1 <=> 10 // -1 10 <=> -1 // 1 // 0, -0 are not the same -0 <=> 0 // -1 0 <=> -0 // 1 ``` ## Use cases ```javascript // Array#sort can use TypedArray#sort default comparison part [10, 5, NaN, -1].sort((a, b) => a <=> b); // [-1, 5, 10, NaN] // desc order new Float64Array([10, 5, NaN, -1]).sort((a, b) => -(a <=> b)); // [NaN, 10, 5, -1] ``` ## Problems `TypedArray#sort` default comparison part has no `string` order function. ```javascript "abc" <=> "def" // same as "abc".localeCompare("def") ? "abc" <=> 42 // same as "abc".localeCompare("42") ? ``` I found the reference to spaceship operator in ES Discuss. It has Already discussed in TC39 meeting? https://esdiscuss.org/topic/informative-notes#content-3 _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
